The present invention relates to a process for removing oxazole impurity from acrylonitrile. The oxazole impurity is commonly formed in the widely used process for production of acrylonitrile by amoxidation of propylene. Acrylonitrile prepared by the invention is useful for the preparation of high quality acrylonitrile polymers or as feed for a catalytic hydration process of acrylonitrile to acrylamide.
In U.S. Pat. Nos. 3,541,131 and 3,574,687, oxazole is removed from acrylonitrile prepared by the amoxidation of propylene. Acrylonitrile containing about 0.3 weight percent water and about 85 ppm oxazole therein is purified by contacting with a water-wet cation exchange resin in the acid form and regenerated with deionized water. U.K. Pat. No. 1,131,134 teaches that oxazole may be removed from acrylonitrile by hydroextractive distillation and U.S. Pat. No. 3,969,344 teaches the purification of polymerizable monomers, acrylonitrile is mentioned, over a porous cation exchange resin of certain pore size and specific surface area which is in the form of the alkali or alkaline earth metal salt thereof. The removal of amine polymerization inhibitors from unsaturated monomers is described in U.S. Pat. No. 2,609,387 by contact with an alcohol dried cation exchange resin in the hydrogen form. The specific examples of monomers so treated are styrene and methyl acrylate while nitriles of acrylic acid are generically described as so treatable. However, the technology for amoxidation of propylene to acrylonitrile was not commercially developed at the time of this teaching and oxazole is not there mentioned as an amine polymerization inhibitor for such monomers.
Other U.S. patents mention purification of acrylonitrile containing methyl vinyl ketone impurities by contact with either cation or anion exchange resins: U.S. Pat. Nos. 3,146,258 and 2,792,415; others mention purification of acrylonitrile with ion exchange resins in conjunction with neutral decolorizing agents such as charcoal beds: U.S. Pat. Nos. 2,444,589 and 2,622,097. The latter of these indicates that water must be added from time to time to rehydrate the beds for effective operation. U.S. Pat. Nos. 2,351,157 and 2,770,645 relate to solution treatments of acrylonitrile to remove impurities therefrom.